There may be needs, for example, for retrieving a specific part of the audio signal representing the recorded discussion of a conference.
Conventionally, for instance, a specific part of the audio signal representing the recorded discussion of a conference and wanted by the user of the record can be retrieved by putting a maker to the specific part at the time of recording so that the user may easily retrieve that part the record any time he or she wants.
There is also known a method of recording a sound signal with counter readings or timings (normally expressed in terms of seconds, minutes and hours) from the start of the recording so that any part of the sound signal has a corresponding numerical value attached to it.
However, the user has to select any of the above methods, be it a method of putting markers or that of recording counter readings, considering what part of the recorded audio signal he or she will have to retrieve and use later. Therefore, these methods are accompanied by the following problems.    1. The user has to carry out an independent and cumbersome operation of putting markers or recording counter readings or timings.    2. The user cannot retrieve any part of the audio signal at which no marker is put or no counter reading is recorded.    3. The part of the signal of a speech of a specific speaker of a conference or a tune of a specific instrument of a concert cannot retrieved. In other words, the speeches of a specific speaker of a conference or the tunes of a specific instrument of a concert cannot be sorted out.    4. Since the proper audio signal has to be recorded with markers or counter readings, it is not possible to retrieve and sort a part of an audio signal by means of a plurality of retrievers without recording it.